The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
Viorel Badescu - One of the best experts on this subject based on the ideXlab platform.
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Smooth and non-smooth optimal pin fin profiles beyond the Schmidt optimality assumption and “Length-of-Arc” approximation
Applied Mathematical Modelling, 2017Co-Authors: Viorel BadescuAbstract:Abstract A parametric model of the pin fin shape has been developed. The pin fin profile optimization is performed without adopting the “Length-of-Arc” approximation. The model is based on the accurate treatment of the Arc Length. The heat transfer coefficient h is not constant but variable along the Length of the pin fin. The objective is to minimize the pin fin volume for given value of the transferred heat flux. Direct optimal control methods are used. The model is validated for a specific case compatible with the application of the Schmidt optimality assumption. Results are shown for pin fins with circular cross section. Both forced convection and natural convection have been considered. Generally, the optimal profile of the pin fin consists of two regions; in the region near the pin fin base, the thickness is constant or decreases almost linearly while in the region near the pin fin tip the thickness is constant or decreases, depending on the thermal load. Including (instead of omitting) in calculation the accurate description of the Arc Length and using variable (instead of constant) h may yield thinner and shorter pin fins. The main conclusion is that, by including in calculation the accurate treatment of the Arc Length, non-smooth pin fin profiles may be obtained. Such profiles consist of a series of steps and are more effective than the smooth profiles.
Leonid Hanin - One of the best experts on this subject based on the ideXlab platform.
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A New Optimum Pin Fin Beyond the “Length-of-Arc” Assumption
Heat Transfer Engineering, 2008Co-Authors: Leonid HaninAbstract:The problem of determining the shape of a minimum volume pin fin that dissipates a given heat flow is solved without imposing the “Length-of-Arc” assumption. Based on the one-dimensional approximation to the temperature distribution and Schmidt's optimality principle, the profile of the optimum pin fin is found to be a circular Arc and geometric parameters of the latter are determined. The volume of the optimum circular pin fin is at least 5.26 times smaller than the volume of the corresponding Schmidt's parabolic pin fin, the best known to date. Equivalently, the optimum circular pin fin dissipates at least 2.71 times larger heat flow than Schmidt's pin fin. The optimum circular pin fin tends to be shorter and have a larger radius at the base than the corresponding Schmidt's fin.
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Efficiency of a New Straight Cooling Fin
Heat Transfer: Volume 4, 2005Co-Authors: Leonid HaninAbstract:In 1926 E. Schmidt [1] discovered his optimum parabolic straight cooling fin. The most critical premise used in his analysis was the “Length-of-Arc” assumption that consists of neglecting the curvature of the fin exposed surface. The problem of optimum straight cooling fin design without the “Length-of-Arc” assumption was solved in [2] which led to the discovery of the optimum circular fin. In the present work, thermal efficiency of this new optimum straight cooling fin is computed.Copyright © 2005 by ASME
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a new minimum volume straight cooling fin taking into account the Length of Arc
International Journal of Heat and Mass Transfer, 2003Co-Authors: Leonid Hanin, Antonio CampoAbstract:Abstract The problem of determining the shape of a straight cooling fin of minimum volume without the “Length of Arc” assumption is addressed. Proceeding from the conventional assumptions of one-dimensionality of the temperature distribution and its linearity for the minimum volume fin we found the profile of the optimum fin to be a circular Arc and computed its geometric parameters. The volume of the optimum circular fin found in this paper is 6.21–8 times smaller than the volume of the corresponding Schmidt’s parabolic optimum fin. The optimum circular fin tends to be shorter and to have a larger base height than Schmidt’s fin.
J. Cheng - One of the best experts on this subject based on the ideXlab platform.
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Equations for the motion of an isolated thin magnetic flux tube
Astronomy and Astrophysics, 1992Co-Authors: J. ChengAbstract:With the Length of Arc as the only independent space variable, the kinematics of thin flux tubes is studied. From the equation of motion of magnetic flux tubes obtained by Spruit (1981, A&A, 98), the intrinsic form of the equation is derived. There is a correction to Spruit's equation in calculating the backreaction on the tube by the surrounding fluid flowing around it
Amir Hasanzadeh - One of the best experts on this subject based on the ideXlab platform.
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Study of Danjon limit in moon crescent sighting
Astrophysics and Space Science, 2012Co-Authors: Amir HasanzadehAbstract:About 70 years ago “André Danjon” a French astrophysicist showed that as elongation of the moon decreases the Arc Length of crescent gets less too. By studying the recent observational data, he concluded that at 7 degree elongation, the Length of Arc (cusp to cusp) will reach zero degree. Today, this value is named as Danjon limit, which points to the limit at which the moon crescent is formed. Danjon believed that the effective factor for occurring this limit was the shadows of moon’s mountains. Later reseArchers have obtained different values for this limit. In this reseArch based on the new data, the decreasing dependence of Length of Arc versus elongation was obtained. The results show that the Danjon limit is about 5 degrees. The effective factors to form the Danjon limit are then given and discussed. By considering the effects of astronomical seeing and shadows of lunar features, the values of the Arc Length were calculated and compared with the observational data curve. The results of this study show good agreement with the observational data. The present reseArch shows that the above-mentioned effects can reduce the Length of Arc. The effect of libration and roughness of the lunar terrain of the moon in forming the moon crescent were also considered, and the possibility of observing thinner crescents by photometric model and breaking the Danjon limit were given.
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Study of Danjon limit in moon crescent sighting
Astrophysics and Space Science, 2012Co-Authors: Amir HasanzadehAbstract:About 70 years ago “Andre Danjon” a French astrophysicist showed that as elongation of the moon decreases the Arc Length of crescent gets less too. By studying the recent observational data, he concluded that at 7 degree elongation, the Length of Arc (cusp to cusp) will reach zero degree. Today, this value is named as Danjon limit, which points to the limit at which the moon crescent is formed. Danjon believed that the effective factor for occurring this limit was the shadows of moon’s mountains. Later reseArchers have obtained different values for this limit. In this reseArch based on the new data, the decreasing dependence of Length of Arc versus elongation was obtained. The results show that the Danjon limit is about 5 degrees. The effective factors to form the Danjon limit are then given and discussed. By considering the effects of astronomical seeing and shadows of lunar features, the values of the Arc Length were calculated and compared with the observational data curve. The results of this study show good agreement with the observational data. The present reseArch shows that the above-mentioned effects can reduce the Length of Arc. The effect of libration and roughness of the lunar terrain of the moon in forming the moon crescent were also considered, and the possibility of observing thinner crescents by photometric model and breaking the Danjon limit were given.
Antonio Campo - One of the best experts on this subject based on the ideXlab platform.
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a new minimum volume straight cooling fin taking into account the Length of Arc
International Journal of Heat and Mass Transfer, 2003Co-Authors: Leonid Hanin, Antonio CampoAbstract:Abstract The problem of determining the shape of a straight cooling fin of minimum volume without the “Length of Arc” assumption is addressed. Proceeding from the conventional assumptions of one-dimensionality of the temperature distribution and its linearity for the minimum volume fin we found the profile of the optimum fin to be a circular Arc and computed its geometric parameters. The volume of the optimum circular fin found in this paper is 6.21–8 times smaller than the volume of the corresponding Schmidt’s parabolic optimum fin. The optimum circular fin tends to be shorter and to have a larger base height than Schmidt’s fin.